Mechanically flexible supercapacitors with fast charge-discharge capacity, high stability and good mechanical properties are essential for powering flexible electronics devices. In this paper, we report a simple process to obtain composite electrode consisting of graphene and polyaniline on stainless steel fabric. The all solid-state flexible supercapacitors based on the composite electrode exhibit a maximal specific capacitance of 1506.6 mF/cm2, and capacitance retention of 92% after 5000 charge-discharge cycles. Furthermore, the bending test shows that the flexible supercapacitor maintains 95.8% of the original capacitance after 1000 bending cycles. The high capacitive performance and anti-bending property of the supercapacitor are ascribed to the favourable microstructure of graphene/polyaniline composite and high flexibility of stainless steel fabric. Our work demonstrates a novel type of high-performance flexible electrode, which will boost the development of flexible and wearable electronics and integrated fabric power devices.